HOUSTON—Paul Hamm’s stay at the top of the U.S. championships might be a short one.

Hamm said he might not compete Saturday after injuring his first hand in the last few seconds of his parallel bars routine, his final event of the night Thursday. As Hamm was flipping to do work on one bar, his right fingers caught on the rail and were jammed to the side. He fell off, and immediately grabbed his wrist as he grimaced.

“I heard a small popping sound in the joint,” said Hamm, who left the arena with his right arm wrapped and will have X-rays Friday morning. “This is not something that will make me sit out of the Olympics, but it might make me sit for Saturday. If it’s something very little, I’ll compete Saturday. If I think it is something worse, I’ll hold off until trials.

“I will not beat up my body and cause more damage just to get to the trials.”

The Olympic trials are June 19-22 in Philadelphia, and Hamm is considered the only lock to make the team—even if he’s not at trials.

Even with the injury, the defending Olympic champion had a commanding lead on his fellow Americans. His score of 93.450 was more than three points ahead of Joseph Hagerty, who had 89.750. Hamm had the highest score on three events, and third-best score on another.

“He was on fire today,” said Jonathan Horton, who was fourth at last year’s world championships. “He was killing it. It’s Paul. He’s a machine.”

But he’s not indestructible.

Only a few gymnasts made it through the night without a fall or major deduction of some sort, and Hamm was seconds away from leading that group. But his fingers got jammed in a “stupid accident.”

“I missed catching with my hand—it’s a skill that’s a little more than I am used to,” Hamm said.

Hamm gripped his right wrist as he talked with coach Miles Avery. But he got back up on the bars and finished the last few seconds of his routine. His face was grim as he walked away from the bars, and twin brother Morgan jumped up on the podium to see if he was OK.

He spent several minutes talking with USA Gymnastics medical officials before two big ice packs were put on his hand. He smiled at one point as he sat with his brother and watched the last few routines, but he was subdued when he was talking with reporters.

“It hurts. It hurts right now because we don’t know what it is,” Avery said. “You’re always more concerned when you don’t know what something is.”

Before the injury, though, Avery said Hamm was as good as he’s seen him.

“Amazing,” Avery said. “He was amazing to watch. Everything he did, all the little things he’s done to improve, he was showing.”